# Standard Deviation of AP Series

Standard Deviation for an Arithmetic Progression (AP) Series can be calculated using a simple formula given below:

${\sigma ^2} = \frac{{\left( {n + 1} \right)\left( {n – 1} \right)}}{{12}}{d^2}$

$\sigma = \sqrt {\frac{{\left( {n + 1} \right)\left( {n – 1} \right)}}{{12}}} \cdot d$

where $$d$$ is the common difference in a AP series.